The proposed work is directed toward elucidation of the path of nascent ribonucleic acid (RNA) across the surface of the bacterial enzyme RNA polymerase. Experiments using azide photoaffinity labels will be performed to determine which subunits of the enzyme are contacted by the growing nucleotide chain and the extent of RNA polymerization at which the path of DNA template diverges from that of RNA. Experiments employing spectroscopic probes will provide complementary information concerning distances between sites on the macromolecular complex and restrictions on the freedom of movement of nascent RNA during the early stages of elongation. "Bifunctional" chelating agents, analogs of ethylenediaminetetraacetic acid which can be attached covalently to biological molecules, will be used as multipurpose spectroscopic probes. These chelating agents can form stable complexes with the ions of approximately 50 metallic elements, providing a wide range of useful spectroscopic properties such as fluorescence, electronic paramagnetism, and correlated gamma-ray cascades.